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Meter slowing down not speeding up... - reply
Posted by Adam on July 3rd, 2009 06:48 AM
In reply to Meter slowing down not speeding up... by BobetteV on October 23rd, 2008 06:26 PM [Go to top of thread]
1 of 1 people found this post helpful
Hi BobetteV
Hi Everyone
I would like to comment problem described in "Meter slowing down not speeding up...".
I am engineer who is familiar with measuring devices like electric meters (analog and electronic), water meters and gas meters, because this devices use magnetic components, which are my daily occupation.
I checked plenty of electrical meters in laboratory in the case of magnetic tampering. From my experience results there is no possibility to speed up electric analog meters without any previous interference!
Analog meters contains magnetic materials in voltage and current measurement circuits. They have rotating an aluminum plate which speeding is balanced by a breaking magnet. This is a main rule for correct accuracy of energy metering. If you remove the breaking magnet, meters will have positive deviation about 2000% (will be extremely speeding). So we have simple deduction, if the breaking magnet will be weaker the aluminum disc will be speeding up.
There is no possibility to destroy breaking magnet by lighting strike as well as the time ageing (16 years is too small), but there are other two possibilities to do this. First: you can do breaking magnet weaker when you expose them to temperature exceeding the Curie temperature for magnet material. Electric analog meters use AlNiCo breaking magnets, which are characterized by Curie temperature at the level of 1200 deg. F. It means the temperature can not be a reason of speeding up, because so big temperature can cause complete destruction of meters.
Second: if you use big external magnetic field in surrounding of breaking magnet of meter, you can demagnetized it. You can do this using min. 2 times stronger magnet than AlNiCo one and it can be only a NdFeB neodymium magnet.
As I mentioned, analog meters use magnetic materials in measurement circuits - current and voltage coils. If you put neodymium magnet in surrounding of this elements you can saturate the magnetic circuits by external magnetic field. This results in lower meter indicating of energy consumption. You should not put neodymium magnet to close to AlNiCo breaking magnet if not, the influence of the strong, external magnet on the meter leads to demagnetizing of its breaking magnet. As a result of this occurrence - after removing the external magnet - the aluminum plates spins faster and the meter characterizes irreversible deviation. This observation is confirmed by my magnetic induction measurements taken from the breaking magnet air gap, before and after applying the magnetic field. The values results 260mT (without the NdFeB magnet) and medium 32mT (after NdFeB magnet applying), respectively.
Unfortunately, people try to cheat and pay less for energy they consume. This is a phenomenon, which is not publicized by electric utilities, because they do not want to give clue to other people how to decrease meters indication. This is also a reason why Bobette had to "...pay over $3000.00, even if the new meter readings show that I am using less electricity than they old one says I am".
Please do not think I accuse Bobette of energy stealing. I do not know this case personally and I am not able to check his meter in laboratory. In the other side if his meter was outside his house, the magnetic tampering could done everyone.
Information about the changes of the measuring characteristic of devices is becoming more easily accessible from many sources: articles, Internet websites and discussion forums. In addition, the great accessibility (e.g. eBay) of neodymium magnets and the low price (because of cheap mass-production from China) influence the phenomenon of illegal media consumption with the use of a strong magnetic field and the problem is rapidly growing.
The described situation is the evidence of the lack of electromagnetic compatibility of measuring devices (concerns also water meters and gas meters). The one way of fight with phenomenon is to detect external magnetic fields. Every utility can do it installing passive magnetic field indicators e.g. MFI-3 type.
I have hope my description will be helpful for you. If you have any additional questions, please reach me at: yhcus7@gmail.com
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